Pre-heat the oven to 150 degrees. Heat 200ml of the milk and add the sliced-open vanilla pod. Boil for 10 minutes.
Leave to cool.
Place 125g of sugar together with the 50ml of water in a saucepan. Bring to a boil and keep boiling until dark golden brown in colour (over 10 minutes or so).
Quickly plunge bottom of the saucepan in cold water, then quickly distribute amongst the 6 ramekins. Swivel around to cover the base of each ramekin.
Whisk the eggs with 3 tbsp sugar, beat in all of the milk. Divide between ramekins.
Fill roasting tin half with boiling water and put the ramekins into it - you want the water to reach half way up the ramekins. Put into the oven for 45 minutes.
Cover and chill overnight.
Turn out before serving.